Constant tension control for elastic filaments



Nov. 9, 1937. A. w. KEEN ET AL 2,093,422

CONSTANT TENSION CONTROL FOR ELASTIC FILAMENTS Filed June 14, 1935ATTORNEY.

Patented Nov. 9, 1937 UNITED STATES PATENT OFFICE ()OlISClAN'J. TENSIONCONTROL FOR ELAS- TIC FILAMENTS Application June 14,

4 Claims.

This invention relates to a constant tension control for elasticfilaments, and more particularly to a tension control for rubber threadas supplied to a covering machine.

Covered elastic yarns in common use in the textile industry for weavingand knitting purposes are not made by covering the rubber core withtextile yarns while the core is relaxed, because for most purposes thiswould produce a finished elastic yarn having very little extensibilityand insufiicient contractlve force or kick". Instead the elastic core iscovered while held under tension at a constant elongation, theelongation and the covering construction being chosen so as to produce afinished elastic yarn having as nearly as possible the desiredextensibility and kick. However, due to small variations in crosssectional area of the elastic core, particularly in the smaller sizes,and also due to slight variations in vulcanization and variations in thetension under which the completed rubber core is wound or spooled, therehas been an unavoidable and relatively wide variation in theextensibility of the finished elastic yarn after it comes from thecovering machine.

An object of the present invention is to provide an apparatus forimparting a constant-tension to a traveling elastic filament.

Another object is to provide an apparatus for imparting a constanttension to an elastic filament as it is unreeled and simultaneouslytherewith controlling its rate of unreeling to correspond.

Y Other objects will appear from the detailed description and drawing,in which latter:

The figure is a more or less diagrammatic view illustrating one form ofthe invention.

In the drawing there is shown an apparatus more particularly designedfor imparting a constant tension to a rubber core as it is unreeled froma spool and fed to a machine for applying coverings to the core.However, it will be obvious that the invention is not limited to suchuse and may be applied generally for use in winding rubber cores orother elastic filaments under a constant tension. I

In the drawing, the numeral I designates a spool of rubber thread, thespindle 2 of which is mounted in slotted guides 2' so that the spool mayrest by gravity on the flanged drum 3 rotatably and slidably mounted onthe drive shaft 4. The shaft a may be clutched in driving relation tothe drum 3 by means of the ball thrust bearing 6 which is slidable onthe shaft 4 and is urged against one end of the hub of drum 3 by 1935,Serial No. 26,542

spring I, and by clutch collar 5 which is fixed on the shaft andfrictionally engages the other end of the hub, thus transmitting thefull driving torque of the shaft to the drum and causing the latter torotate at the speed of the shaft. Spring 1 is retained on the shaft bycollar 1" fixed to the shaft.

In order to controllably retard the speed of the drum relative to theshaft, or to stop the rotation of the drum altogether, there is provideda brake operated by a fluid pressure controlled bellows. The bellows 8carries a friction member 8 at its free end adapted to engage the flangeof drum 3, the other end of the bellows being fixedly mounted on asupport 9. In the inoperative position of the brake, the bellows isdeflated and the friction member 8' is disengaged from the drum. Inoperative position, the bellows isat least partially inflated and urgesfriction member 8' against the flange of drum 3 in such a direction asto oppose the thrust of bearing 6 against the drum, thus partially orcompletely releasing the drum from engagement with collar 5. It is seenthat, by controlling the fluid pressure in the bellows, the brakingaction of the friction member 8' on the flange of the drum and thedegree of slippage between the drum hub and collar 5 may be controlledso that the drum will rotate at any required intermediate speed.

By reason of the gravity support of the spool l on the drum 3, therubber thread will be unreeled from the spool at the peripheral speed ofthe drum 3, irrespective of the size of the package of rubber thread onthe spool. I

Communicating with the bellows 8 through a pipe I is a pressure controlchamber i l to which air or other fluid is supplied under constantpressure by supply pipe I2 and reduced nozzle l3. Also leading from thechamber II is an air-leak pipe M, the reduced end of which may bepartially or completely closed by the pivoted valve lever l5, thusproviding control of the pressure in chamber II and hence of thepressure in bellows 8. In the drawing there is shown in full lines forillustration purposes one position which the parts may assume, with thevalve lever l completely closing the end of the air leak pipe M, thebrake 8 fully engaging the flange of drum 3, and the drum entirelywithdrawn from contact with clutch collar 5.

The rubber thread 16, upon delivery from the spool I is led around afixed guide pulley l1 and then around the floating pulley I8, whichlatter by means of the rod I9 carries the variably fixed weights 20. Therubber thread l6 after leaving the floating pulley It then passes aroundthe flxed guide pulley 2| and thence to the covering apparatus or awindup reel orspool. IQ of the pulley 18 passes through an opening 22 inthe pivoted valve lever l5.

In operation it will be seen that by varying the number of weights 20the desired amount of tension may be placed upon the rubber thread i5and by reason of the floating character of the pulley 18, this tensionwillbe constant, regardless of the length of the suspended loop ofthread. If, by reason of any variation in cross section of the rubberthread, or in its degree of vulcanization or its winding tension, thereis any change in the elongation of the thread l6 as it is delivered fromthe spool I, there will be a corresponding change in the length of thesuspended loop of thread. This will cause the pulley l8 to rise or falldepending upon whether the thread l6 decreases or increases in itselongation. Upon any decrease in elongation suflicient to lift theweights 20 into contact with the pivoted valve lever l5, theair-leakvalve at the end of pipe I4 will at least be partially opened and theair pressure in the bellows 8 will accordingly be reduced, permittingthe bellows to deflate and thus reducing the braking action of the brake8' on the drum 3. When this occurs the spring I and thrust bearing 6operate to increase the thrust oi. the drum hub against collar 5,whereby a greater driving torque is transmitted to the drum, and thespeed of rotation of the drum and accordingly that of the spool l isincreased. The resulting increase in the rate of delivery of thread fromthe spool thus compensates for the decrease in its elongation. Upon anincrease in the length of the suspended loop of thread, the weights 20drop, the valve lever l5 closes the air-leak valve, the fluid pressurein the bellows 8 is increased and the bellows expands, thereby causingthe brake 8' to engage the flange of the .drum 3, thus retarding itsrotation and also at least partially releasing the driving'engagemeritbetween the collar 5 and the drum. The resulting decrease in the rate ofdelivery of thread from the spool thus compensates for the increase inits elongation.

In normal operation of the mechanism the airleak valve remains in apartly closed position which varies slightly according to variations inthe elongation of the thread, thus effecting a continuous throttlingcontrol on the brake and clutch. The mechanism is instantly responsiveto slight variations in the elongation of the thread, and accordinglythe rate at which thread is unwound from the spool is so accuratelycontrolled that the length of the suspended loop of thread remainssubstantially constant. Obviously, the smoothness with which thethrottling action operates may be increased by increasing the leverageratio of lever l5.

In the following table there are shown the results obtained with twodiiferent constructions of covered elastic yarn, a portion of eachconstruction having been covered by the prior art procedure and anotherportion havingv been covered with the use of the tension control of thepresent invention. ,In constructionA there threads laid side by sidewill measure one inch across. In this construction the inner and outercoverings were oppositely helically wrapped on The rod the tensionedcore and each covering was of two ends of 140/1 cotton yarn.

In construction B the elastic core was of rubber deposited directly fromlatex and of size 's; the inner cover was of one end of 50/1 cotton yarnwhile the outer cover was of 2 ends of 100/1 cotton yarn.

In order to secure as great uniformity as possible, rubber thread fromfour different spools was used in the covering of each construction. Thecovering was done on two adjacent spindles of the same machine, oneequipped with the regular let-off and the other equipped with the coretension control of the present invention. The finished yarns were testedat regular intervals along their lengths by hanging a 6% oz weight on a5" loop (10 inch length) 01 the yarn and measuring the elongation. Thefrequency oi. occurrence of various elongations is shown in thefollowing table, but as the elongations of the series shown in the tablediffer by 5% and the actual elongations measured sometimes diflered byless than this amount, the tests at each elongation in the table includethose differing by plus or minus 2 /2% from the specified one.

Construction "A It will be seen from the table that, in the case of yarnof construction A, the yarn made in the usual manner varied inelongation values over a range of 30% while the yarn made by the use ofthe present invention varied in elongation values over a range of only15%. I! 135% elongation be taken as the norm in the usual construction,then in only 19 tests or 34.5% of the total was the elongation within2%% of the norm, while taking 140% elongation as the norm for yarn madeby the invention, then in 33 tests or 60% of the total the elongationwas within 2%% of the norm.

In the case of yarn of construction B, the yarn made in the usual mannervaried in elongation values over a range of 35%, while the yarn inade bythe use of the invention varied in elongation values over a range ofonly 25%. It or elongation be taken as the norm in the usualconstruction, then in only 29 tests or 29% of the total was theelongation within 2 /2% of the norm, while taking 100% elongation as thenorm for yarn made by the invention, then in 48 tests or 47.5% of thetotal the elongation was within 2 of the norm.

It will be seen from the above that by the use of the invention theuniformity in elongation of the covered thread has been greatlyincreased, and thereby variation in fabrics employing the coveredelastic thread is greatly reduced.

While the invention has been specifically described in connection withthe covering of a rubber core to make elastic yarns, it is obvious, as

before pointed out, that it is also capable 01' use in winding rubberthread, or elastic filaments in general, under a uniform tension.

Having thus described our invention, what we claim and desire to protectby Letters Patent is:

1. A constant tension control for elastic filaments comprising supplymeans for delivering the filament, a weighted element adapted to bemovably supported by the delivered filament, a bellows for controllingdelivery from said supply means, means for supplying a gaseous mediumunder pressure. to said bellows, a relief valve for the bellows, andmeans actuated by said weighted element for operating said valve.

2. A constant tension control for filaments, comprising a spool for thefilament, rotary drive means for unwinding the filament from said spool,a drive shaft, a clutch for driving said drive means from said shaft, abrake operable to engage and shift said drive means along said shaftaway from the clutch to release said clutch, and means for controllingthe brake from said filament, said brake and clutch being constructedand arranged whereby as the pressure of the brake against said drivemeans is increased the latter will be forced away from said clutch.

3. A constant tension control for filaments,

- comprising a spool for the filament, a drive shaft,

a spool driving drum rotatably and slidably mounted upon said shaft, aclutch for driving the drum from said shaft, a brake adaptedto engagesaid drum and move it away from said clutch, and means for controllingthe brake from said filament whereby as the brake action is increasedthe clutch action will be decreased.

4. A constant tension control for filaments, comprising a spool for thefilament, a drive shaft, a spool driving drum rotatably and slidablymounted upon said shaft, a clutch for driving the drum from said shaft,a brake adapted to engage said drum and move it away from said clutch,and fiuid pressure mechanism for operating said brake and controlled bythe delivered filament whereby as the brake action is increased theclutch action will be decreased.

ALEXIS W. KEEN.

FAYETTE D. CHITI'EN'DEN.

